The gray squirrels are chewing off the ash leaves. https://animals.mom.me/squirrels-chew-branches-10135.html
We do not have any grey squirrels, we do have ia few red squirrels, do they also chew off the leaves?
It is usually gray squirrels that chew off leaves. Do you see any black spots on the leaves? Another reason that your Ash tree might be losing its leaves is that the tree has a fungal disease called Anthracnose. Anthracnose or Discula fraxinea is a fungal disease of ash trees that causes tan to brown irregular spots on leaves. In severe infection, the ash leaves may curl, wilt, and fall off. Our recent cool wet spring weather creates ideal conditions for the young leaves to be infected. Trees will produce a second growth of leaves by midsummer when leaf drop occurs. Anthracnose is not a significant threat to the health of the tree and doesn’t require treatment.